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Cells
Light Microscopes
Lenses bend light, magnifying and focusing the
image.
Anton Van Leeuwenhoek
Simple Microscope: has one lens
Example: magnifying glass
Compound Microscope: has more than one lens
Example: modern microscope can magnify 400X
Microscopes
Electron microscopes
Electron microscopes use a beam of electrons to create the image.
The beam of electrons is focused by a magnetic field. Magnification is
up to one million times and the specimen is usually dead.
Scanning Electron Microscope (SEM)
-electron beam scans surface
-gives a picture of the outside
Transmission Electron Microscopes (TEM)
-electron beams pass
through the specimen
-gives a cross section view
Types of Microscopy
Light Microscopy
Human Cheek Cell
Electron Microscopy
Plant Root Cell
Scanning Electron Microscopy
White Blood Cell
With fluorescent dyes.
SEM
Nerve Cell
SEM
Skin Cell
http://learn.genetics.utah.edu/content/begin/
cells/scale/
http://www.cellsalive.com/howbig_js.htm
Cell Size
0.2 micrometers
Mycoplasma bacteria
Average
5-50
micrometers
10 centimeters
Ostrich Egg
Cells are either simple prokaryotes or
complex eukaryotes.
Prokaryote or Eukaryote?
Prokaryote
Small
Simple
No nucleus, no
organelles
Eukaryote
Large
Complex internal
structures (organelles)
Nucleus
Who is a prokaryote?
Who is a eukaryote?
BACTERIA
Protists
Fungi
Plants
Animals (humans too!)
Types of Eukaryotic Cells
Plant Cell
Animal Cell
Protozoa Cell
(paramecium)
The Discovery of the Microscope Lead To the Discovery of Cells
History
*Anton von Leewenhoek discovered the microscope
*Robert Hooke discovered cells and named them
Further Discoveries:
Matthias Schleiden- All plants are made of cells.
Theodor Schwann- All animals are made of cells.
Rudolf Virchow- All cells come from existing cells.
Cell Theory
1) All living things are made up of cells.
2) Cells are the basic unit of structure and function
in living things.
3) New cells are produced from existing cells.
Structures Found in All Cells
Cell membrane
Genetic material
Cytoplasm
Ribosomes
Cell Membrane
Made of phospholipids and proteins.
Functions :
1. Regulates what enters and leaves the cell.
selectively permeable
2. Support
3. Protection
Phospholipid
Attracted
To Water
Repelled
By Water
Phospholipid Bilayer
Phosphate “heads” are attracted to water
(hydrophilic). They are oriented to the OUTSIDE
of the cell membrane bilayer.
Fatty acid “tails” are repelled by water
(hydrophobic). They move to the INSIDE
of the cell membrane bilayer.
Cell membrane:
-all cells have this structure
-made of lipid bilayer
-embedded proteins (act as channels & pumps)
The Fluid Mosaic Model
Various macromolecules “float” in the lipid bilayer forming a “mosaic”.
Cytoplasm
Found in all cells.
Clear, thick watery material.
Provides support for the cell contents.
cytoplasm
Ribosomes
a. Function: make proteins
b. Structure: composed of protein and rRNA
c. Found in 2 places in the cell
-in the cytoplasm
-rough ER.
Surrounds the cell membrane
Nucleus
(found only in eukaryotic cells)
Functions:
1. Cell control
2. Stores genetic
material
-nuclear envelope
-genetic material
-nucleolus
Mitochondria
Function : Breaks down sugar to release energy (ATP)
Structure: Two membranes. The inner membrane is folded.
Interesting Facts: The mitochondria has its own chromosome.
Chloroplast
Function: Photosynthesis, converts energy from the sun into
chemical energy (sugar)
Structure: two outer membranes
thylakoids
Interesting Fact: The chloroplast has its own chromosome.
Endoplasmic Reticulum
Functions: site of protein and lipid synthesis
Structure: made of folded membranes, network of tubes
Smooth ER (SER): NO ribosomes, makes lipids
Rough ER (RER): ribosomes, makes proteins
Golgi Apparatus
Structure: stacks of membrane sacs
Function:
-processes and packages proteins and lipid made in the ER
-sends them to their proper location
Vacuoles
Function: Store food, water and wastes
Structure: Fluid filled membrane sacs
Animal Cell
Many small
vacuoles
Plant Cell
One large
vacuole
Lysosomes
Found only in animal cells.
Function: Break down food and old cell parts
Structure: Small, round membrane sacs with digestive enzymes.
How did the first eukaryotes evolve?
Or
Where did organelles come from?
Eukaryotic Cells evolved from a combination of different prokaryotic cells.
The Endosymbiotic Theory
Endosymbiosis – One organism engulfs another but does not digest
it. Instead, they work together.
Mitochondria, chloroplasts originated through endosymbiosis.
These organelles started as free-living bacteria that were taken
inside another prokaryotic cell.
Mitochondria developed from proteobacteria and chloroplasts from
cyanobacteria.
Eukaryotic cells evolved
from a combination of
different prokaryotic cells.
http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter4/
animation_-_endosymbiosis.html
Evidence for the Endosymbiotic Theory
1) Mitochondria and chloroplasts have their own DNA.
2) These organelles have two outer membranes.
3) These organelles are the same size as the
prokaryotes from which they originated.
Path Of A New Protein Inside the Cell